360 ABSTRACTS OF SCIENTIFIC PAPERS 



magnitude ; of capacity and specific inductive capacity ; of potential ; 

 of the division of potential by resistance slides, and the combination 

 of two slides to give minute subdivision ; of the measurement of 

 potential by electrometers. The lectures conclude with a detailed 

 account of the tests employed during the laying of the 1866 Atlantic 

 Cable, with diagrams showing the electrical arrangements on shore 

 and on the ship. 



XXII. On the Submersion and Recovery of Submarine Cables. 

 1 Proceedings of the Royal Institution,' May 21, 1869 (Abstract). 



This lecture describes the general construction of deep-sea cables, 

 with special reference to the French Atlantic Cable of 1869, parti- 

 culars of which are stated numerically in full. An account is given 

 of the arrangements for coiling on board the ' Great Eastern,' and for 

 paying out the cable. It is shown how the strains to be expected 

 during the laying are calculated. The cable, while sinking, meets 

 with a resistance in a direction normal to its length, equal (for the 

 Atlantic Cable) to O154 v 2 per foot of length, v being the velocity of 

 sinking, measured in a direction normal to the length of the cable. 

 Its weight being 0'2575 Ibs. per foot the velocity of settling is given 

 by the equation 



0-154v 2 =0-2575. 



The result of this resistance is that the cable lies in a straight line, 

 the inclination of which depends on the velocity of the ship and on v. 

 A formula for the inclination is given, and it is mentioned that the 

 rough Atlantic cable, when the ship was going at the speed of six knots 

 per hour, lay at an angle of 6|, so that the inclined plane was seven- 

 teen miles long, and each piece of the cable took nearly three hours to 

 reach the bottom. The stress on the cable at the top is less than the 

 weight of a length hanging plumb from the surface to the bottom, by 

 the resistance which the rope meets in slipping down along the plane 

 a quantity depending on the amount of slack paid out. A formula 

 and coefficient, applicable to the Atlantic Cable, are given for this 

 resistance, and the stresses are calculated in particular examples. 

 The process of grappling is described. Figures are given for the 

 stresses which occur during the recovery of cables laid with assumed 

 percentages of slack ; and the conclusion is stated that the strength 

 of the cable is from three to four times greater than the strain which 

 in fair weather need come on the cable when being picked up from 

 a depth of two miles. 



